1 use super::attr::InnerAttrForbiddenReason;
2 use super::diagnostics::AttemptLocalParseRecovery;
3 use super::expr::LhsExpr;
4 use super::pat::RecoverComma;
5 use super::path::PathStyle;
6 use super::TrailingToken;
8 AttrWrapper, BlockMode, FnParseMode, ForceCollect, Parser, Restrictions, SemiColonMode,
11 AssignmentElseNotAllowed, CompoundAssignmentExpressionInLet, ConstLetMutuallyExclusive,
12 DocCommentDoesNotDocumentAnything, ExpectedStatementAfterOuterAttr, InvalidCurlyInLetElse,
13 InvalidExpressionInLetElse, InvalidIdentiferStartsWithNumber, InvalidVariableDeclaration,
14 InvalidVariableDeclarationSub, WrapExpressionInParentheses,
16 use crate::maybe_whole;
19 use rustc_ast::ptr::P;
20 use rustc_ast::token::{self, Delimiter, TokenKind};
21 use rustc_ast::util::classify;
22 use rustc_ast::{AttrStyle, AttrVec, LocalKind, MacCall, MacCallStmt, MacStmtStyle};
23 use rustc_ast::{Block, BlockCheckMode, Expr, ExprKind, HasAttrs, Local, Stmt};
24 use rustc_ast::{StmtKind, DUMMY_NODE_ID};
25 use rustc_errors::{Applicability, DiagnosticBuilder, ErrorGuaranteed, PResult};
26 use rustc_span::source_map::{BytePos, Span};
27 use rustc_span::symbol::{kw, sym};
32 /// Parses a statement. This stops just before trailing semicolons on everything but items.
33 /// e.g., a `StmtKind::Semi` parses to a `StmtKind::Expr`, leaving the trailing `;` unconsumed.
34 // Public for rustfmt usage.
35 pub fn parse_stmt(&mut self, force_collect: ForceCollect) -> PResult<'a, Option<Stmt>> {
36 Ok(self.parse_stmt_without_recovery(false, force_collect).unwrap_or_else(|mut e| {
38 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
43 /// If `force_collect` is [`ForceCollect::Yes`], forces collection of tokens regardless of whether
44 /// or not we have attributes
45 pub(crate) fn parse_stmt_without_recovery(
48 force_collect: ForceCollect,
49 ) -> PResult<'a, Option<Stmt>> {
50 let attrs = self.parse_outer_attributes()?;
51 let lo = self.token.span;
53 // Don't use `maybe_whole` so that we have precise control
54 // over when we bump the parser
55 if let token::Interpolated(nt) = &self.token.kind && let token::NtStmt(stmt) = &**nt {
56 let mut stmt = stmt.clone();
58 stmt.visit_attrs(|stmt_attrs| {
59 attrs.prepend_to_nt_inner(stmt_attrs);
61 return Ok(Some(stmt.into_inner()));
64 if self.token.is_keyword(kw::Mut) && self.is_keyword_ahead(1, &[kw::Let]) {
66 let mut_let_span = lo.to(self.token.span);
67 self.sess.emit_err(InvalidVariableDeclaration {
69 sub: InvalidVariableDeclarationSub::SwitchMutLetOrder(mut_let_span),
73 Ok(Some(if self.token.is_keyword(kw::Let) {
74 self.parse_local_mk(lo, attrs, capture_semi, force_collect)?
75 } else if self.is_kw_followed_by_ident(kw::Mut) && self.may_recover() {
76 self.recover_stmt_local_after_let(lo, attrs, InvalidVariableDeclarationSub::MissingLet)?
77 } else if self.is_kw_followed_by_ident(kw::Auto) && self.may_recover() {
78 self.bump(); // `auto`
79 self.recover_stmt_local_after_let(
82 InvalidVariableDeclarationSub::UseLetNotAuto,
84 } else if self.is_kw_followed_by_ident(sym::var) && self.may_recover() {
86 self.recover_stmt_local_after_let(
89 InvalidVariableDeclarationSub::UseLetNotVar,
91 } else if self.check_path() && !self.token.is_qpath_start() && !self.is_path_start_item() {
92 // We have avoided contextual keywords like `union`, items with `crate` visibility,
93 // or `auto trait` items. We aim to parse an arbitrary path `a::b` but not something
94 // that starts like a path (1 token), but it fact not a path.
95 // Also, we avoid stealing syntax from `parse_item_`.
96 if force_collect == ForceCollect::Yes {
97 self.collect_tokens_no_attrs(|this| this.parse_stmt_path_start(lo, attrs))
99 self.parse_stmt_path_start(lo, attrs)
101 } else if let Some(item) = self.parse_item_common(
105 FnParseMode { req_name: |_| true, req_body: true },
108 // FIXME: Bad copy of attrs
109 self.mk_stmt(lo.to(item.span), StmtKind::Item(P(item)))
110 } else if self.eat(&token::Semi) {
111 // Do not attempt to parse an expression if we're done here.
112 self.error_outer_attrs(attrs);
113 self.mk_stmt(lo, StmtKind::Empty)
114 } else if self.token != token::CloseDelim(Delimiter::Brace) {
115 // Remainder are line-expr stmts.
116 let e = if force_collect == ForceCollect::Yes {
117 self.collect_tokens_no_attrs(|this| {
118 this.parse_expr_res(Restrictions::STMT_EXPR, Some(attrs))
121 self.parse_expr_res(Restrictions::STMT_EXPR, Some(attrs))
123 if matches!(e.kind, ExprKind::Assign(..)) && self.eat_keyword(kw::Else) {
124 let bl = self.parse_block()?;
125 // Destructuring assignment ... else.
126 // This is not allowed, but point it out in a nice way.
127 self.sess.emit_err(AssignmentElseNotAllowed { span: e.span.to(bl.span) });
129 self.mk_stmt(lo.to(e.span), StmtKind::Expr(e))
131 self.error_outer_attrs(attrs);
136 fn parse_stmt_path_start(&mut self, lo: Span, attrs: AttrWrapper) -> PResult<'a, Stmt> {
137 let stmt = self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
138 let path = this.parse_path(PathStyle::Expr)?;
140 if this.eat(&token::Not) {
141 let stmt_mac = this.parse_stmt_mac(lo, attrs, path)?;
142 if this.token == token::Semi {
143 return Ok((stmt_mac, TrailingToken::Semi));
145 return Ok((stmt_mac, TrailingToken::None));
149 let expr = if this.eat(&token::OpenDelim(Delimiter::Brace)) {
150 this.parse_struct_expr(None, path, true)?
152 let hi = this.prev_token.span;
153 this.mk_expr(lo.to(hi), ExprKind::Path(None, path))
156 let expr = this.with_res(Restrictions::STMT_EXPR, |this| {
157 this.parse_dot_or_call_expr_with(expr, lo, attrs)
159 // `DUMMY_SP` will get overwritten later in this function
160 Ok((this.mk_stmt(rustc_span::DUMMY_SP, StmtKind::Expr(expr)), TrailingToken::None))
163 if let StmtKind::Expr(expr) = stmt.kind {
164 // Perform this outside of the `collect_tokens_trailing_token` closure,
165 // since our outer attributes do not apply to this part of the expression
166 let expr = self.with_res(Restrictions::STMT_EXPR, |this| {
167 this.parse_assoc_expr_with(
169 LhsExpr::AlreadyParsed { expr, starts_statement: true },
172 Ok(self.mk_stmt(lo.to(self.prev_token.span), StmtKind::Expr(expr)))
178 /// Parses a statement macro `mac!(args)` provided a `path` representing `mac`.
179 /// At this point, the `!` token after the path has already been eaten.
180 fn parse_stmt_mac(&mut self, lo: Span, attrs: AttrVec, path: ast::Path) -> PResult<'a, Stmt> {
181 let args = self.parse_delim_args()?;
182 let delim = args.delim.to_token();
183 let hi = self.prev_token.span;
185 let style = match delim {
186 Delimiter::Brace => MacStmtStyle::Braces,
187 _ => MacStmtStyle::NoBraces,
190 let mac = P(MacCall { path, args, prior_type_ascription: self.last_type_ascription });
192 let kind = if (style == MacStmtStyle::Braces
193 && self.token != token::Dot
194 && self.token != token::Question)
195 || self.token == token::Semi
196 || self.token == token::Eof
198 StmtKind::MacCall(P(MacCallStmt { mac, style, attrs, tokens: None }))
200 // Since none of the above applied, this is an expression statement macro.
201 let e = self.mk_expr(lo.to(hi), ExprKind::MacCall(mac));
202 let e = self.maybe_recover_from_bad_qpath(e)?;
203 let e = self.parse_dot_or_call_expr_with(e, lo, attrs)?;
204 let e = self.parse_assoc_expr_with(
206 LhsExpr::AlreadyParsed { expr: e, starts_statement: false },
210 Ok(self.mk_stmt(lo.to(hi), kind))
213 /// Error on outer attributes in this context.
214 /// Also error if the previous token was a doc comment.
215 fn error_outer_attrs(&self, attrs: AttrWrapper) {
217 && let attrs = attrs.take_for_recovery(self.sess)
218 && let attrs @ [.., last] = &*attrs {
219 if last.is_doc_comment() {
220 self.sess.emit_err(DocCommentDoesNotDocumentAnything {
224 } else if attrs.iter().any(|a| a.style == AttrStyle::Outer) {
225 self.sess.emit_err(ExpectedStatementAfterOuterAttr { span: last.span });
230 fn recover_stmt_local_after_let(
234 subdiagnostic: fn(Span) -> InvalidVariableDeclarationSub,
235 ) -> PResult<'a, Stmt> {
237 self.collect_tokens_trailing_token(attrs, ForceCollect::Yes, |this, attrs| {
238 let local = this.parse_local(attrs)?;
239 // FIXME - maybe capture semicolon in recovery?
241 this.mk_stmt(lo.to(this.prev_token.span), StmtKind::Local(local)),
245 self.sess.emit_err(InvalidVariableDeclaration { span: lo, sub: subdiagnostic(lo) });
254 force_collect: ForceCollect,
255 ) -> PResult<'a, Stmt> {
256 self.collect_tokens_trailing_token(attrs, force_collect, |this, attrs| {
257 this.expect_keyword(kw::Let)?;
258 let local = this.parse_local(attrs)?;
259 let trailing = if capture_semi && this.token.kind == token::Semi {
264 Ok((this.mk_stmt(lo.to(this.prev_token.span), StmtKind::Local(local)), trailing))
268 /// Parses a local variable declaration.
269 fn parse_local(&mut self, attrs: AttrVec) -> PResult<'a, P<Local>> {
270 let lo = self.prev_token.span;
272 if self.token.is_keyword(kw::Const) && self.look_ahead(1, |t| t.is_ident()) {
273 self.sess.emit_err(ConstLetMutuallyExclusive { span: lo.to(self.token.span) });
277 self.report_invalid_identifier_error()?;
278 let (pat, colon) = self.parse_pat_before_ty(None, RecoverComma::Yes, "`let` bindings")?;
280 let (err, ty) = if colon {
281 // Save the state of the parser before parsing type normally, in case there is a `:`
282 // instead of an `=` typo.
283 let parser_snapshot_before_type = self.clone();
284 let colon_sp = self.prev_token.span;
285 match self.parse_ty() {
286 Ok(ty) => (None, Some(ty)),
288 if let Ok(snip) = self.span_to_snippet(pat.span) {
289 err.span_label(pat.span, format!("while parsing the type for `{}`", snip));
291 // we use noexpect here because we don't actually expect Eq to be here
292 // but we are still checking for it in order to be able to handle it if
294 let err = if self.check_noexpect(&token::Eq) {
298 // Rewind to before attempting to parse the type and continue parsing.
299 let parser_snapshot_after_type =
300 mem::replace(self, parser_snapshot_before_type);
301 Some((parser_snapshot_after_type, colon_sp, err))
309 let init = match (self.parse_initializer(err.is_some()), err) {
310 (Ok(init), None) => {
311 // init parsed, ty parsed
314 (Ok(init), Some((_, colon_sp, mut err))) => {
315 // init parsed, ty error
316 // Could parse the type as if it were the initializer, it is likely there was a
317 // typo in the code: `:` instead of `=`. Add suggestion and emit the error.
318 err.span_suggestion_short(
320 "use `=` if you meant to assign",
322 Applicability::MachineApplicable,
325 // As this was parsed successfully, continue as if the code has been fixed for the
326 // rest of the file. It will still fail due to the emitted error, but we avoid
330 (Err(init_err), Some((snapshot, _, ty_err))) => {
331 // init error, ty error
333 // Couldn't parse the type nor the initializer, only raise the type error and
334 // return to the parser state before parsing the type as the initializer.
335 // let x: <parse_error>;
339 (Err(err), None) => {
340 // init error, ty parsed
341 // Couldn't parse the initializer and we're not attempting to recover a failed
342 // parse of the type, return the error.
346 let kind = match init {
347 None => LocalKind::Decl,
349 if self.eat_keyword(kw::Else) {
350 if self.token.is_keyword(kw::If) {
351 // `let...else if`. Emit the same error that `parse_block()` would,
352 // but explicitly point out that this pattern is not allowed.
353 let msg = "conditional `else if` is not supported for `let...else`";
354 return Err(self.error_block_no_opening_brace_msg(msg));
356 let els = self.parse_block()?;
357 self.check_let_else_init_bool_expr(&init);
358 self.check_let_else_init_trailing_brace(&init);
359 LocalKind::InitElse(init, els)
361 LocalKind::Init(init)
365 let hi = if self.token == token::Semi { self.token.span } else { self.prev_token.span };
366 Ok(P(ast::Local { ty, pat, kind, id: DUMMY_NODE_ID, span: lo.to(hi), attrs, tokens: None }))
369 /// report error for `let 1x = 123`
370 pub fn report_invalid_identifier_error(&mut self) -> PResult<'a, ()> {
371 if let token::Literal(lit) = self.token.uninterpolate().kind &&
372 rustc_ast::MetaItemLit::from_token(&self.token).is_none() &&
373 (lit.kind == token::LitKind::Integer || lit.kind == token::LitKind::Float) &&
374 self.look_ahead(1, |t| matches!(t.kind, token::Eq) || matches!(t.kind, token::Colon ) ) {
375 return Err(self.sess.create_err(InvalidIdentiferStartsWithNumber { span: self.token.span }));
380 fn check_let_else_init_bool_expr(&self, init: &ast::Expr) {
381 if let ast::ExprKind::Binary(op, ..) = init.kind {
383 self.sess.emit_err(InvalidExpressionInLetElse {
385 operator: op.node.to_string(),
386 sugg: WrapExpressionInParentheses {
387 left: init.span.shrink_to_lo(),
388 right: init.span.shrink_to_hi(),
395 fn check_let_else_init_trailing_brace(&self, init: &ast::Expr) {
396 if let Some(trailing) = classify::expr_trailing_brace(init) {
397 self.sess.emit_err(InvalidCurlyInLetElse {
398 span: trailing.span.with_lo(trailing.span.hi() - BytePos(1)),
399 sugg: WrapExpressionInParentheses {
400 left: trailing.span.shrink_to_lo(),
401 right: trailing.span.shrink_to_hi(),
407 /// Parses the RHS of a local variable declaration (e.g., `= 14;`).
408 fn parse_initializer(&mut self, eq_optional: bool) -> PResult<'a, Option<P<Expr>>> {
409 let eq_consumed = match self.token.kind {
410 token::BinOpEq(..) => {
411 // Recover `let x <op>= 1` as `let x = 1`
412 self.sess.emit_err(CompoundAssignmentExpressionInLet { span: self.token.span });
416 _ => self.eat(&token::Eq),
419 Ok(if eq_consumed || eq_optional { Some(self.parse_expr()?) } else { None })
422 /// Parses a block. No inner attributes are allowed.
423 pub(super) fn parse_block(&mut self) -> PResult<'a, P<Block>> {
424 let (attrs, block) = self.parse_inner_attrs_and_block()?;
425 if let [.., last] = &*attrs {
426 self.error_on_forbidden_inner_attr(
428 super::attr::InnerAttrPolicy::Forbidden(Some(
429 InnerAttrForbiddenReason::InCodeBlock,
436 fn error_block_no_opening_brace_msg(
439 ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
440 let sp = self.token.span;
441 let mut e = self.struct_span_err(sp, msg);
442 let do_not_suggest_help = self.token.is_keyword(kw::In) || self.token == token::Colon;
444 // Check to see if the user has written something like
449 // which is valid in other languages, but not Rust.
450 match self.parse_stmt_without_recovery(false, ForceCollect::No) {
451 // If the next token is an open brace, e.g., we have:
453 // if expr other_expr {
454 // ^ ^ ^- lookahead(1) is a brace
455 // | |- current token is not "else"
456 // |- (statement we just parsed)
458 // the place-inside-a-block suggestion would be more likely wrong than right.
460 // FIXME(compiler-errors): this should probably parse an arbitrary expr and not
461 // just lookahead one token, so we can see if there's a brace after _that_,
462 // since we want to protect against:
463 // `if 1 1 + 1 {` being suggested as `if { 1 } 1 + 1 {`
466 if (!self.token.is_keyword(kw::Else)
467 && self.look_ahead(1, |t| t == &token::OpenDelim(Delimiter::Brace)))
468 || do_not_suggest_help => {}
469 // Do not suggest `if foo println!("") {;}` (as would be seen in test for #46836).
470 Ok(Some(Stmt { kind: StmtKind::Empty, .. })) => {}
472 let stmt_own_line = self.sess.source_map().is_line_before_span_empty(sp);
473 let stmt_span = if stmt_own_line && self.eat(&token::Semi) {
474 // Expand the span to include the semicolon.
475 stmt.span.with_hi(self.prev_token.span.hi())
479 e.multipart_suggestion(
480 "try placing this code inside a block",
482 (stmt_span.shrink_to_lo(), "{ ".to_string()),
483 (stmt_span.shrink_to_hi(), " }".to_string()),
485 // Speculative; has been misleading in the past (#46836).
486 Applicability::MaybeIncorrect,
490 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
495 e.span_label(sp, "expected `{`");
499 fn error_block_no_opening_brace<T>(&mut self) -> PResult<'a, T> {
500 let tok = super::token_descr(&self.token);
501 let msg = format!("expected `{{`, found {}", tok);
502 Err(self.error_block_no_opening_brace_msg(&msg))
505 /// Parses a block. Inner attributes are allowed.
506 pub(super) fn parse_inner_attrs_and_block(&mut self) -> PResult<'a, (AttrVec, P<Block>)> {
507 self.parse_block_common(self.token.span, BlockCheckMode::Default, true)
510 /// Parses a block. Inner attributes are allowed.
511 pub(super) fn parse_block_common(
514 blk_mode: BlockCheckMode,
515 can_be_struct_literal: bool,
516 ) -> PResult<'a, (AttrVec, P<Block>)> {
517 maybe_whole!(self, NtBlock, |x| (AttrVec::new(), x));
519 let maybe_ident = self.prev_token.clone();
520 self.maybe_recover_unexpected_block_label();
521 if !self.eat(&token::OpenDelim(Delimiter::Brace)) {
522 return self.error_block_no_opening_brace();
525 let attrs = self.parse_inner_attributes()?;
526 let tail = match self.maybe_suggest_struct_literal(
530 can_be_struct_literal,
533 None => self.parse_block_tail(lo, blk_mode, AttemptLocalParseRecovery::Yes)?,
538 /// Parses the rest of a block expression or function body.
539 /// Precondition: already parsed the '{'.
540 pub(crate) fn parse_block_tail(
544 recover: AttemptLocalParseRecovery,
545 ) -> PResult<'a, P<Block>> {
546 let mut stmts = vec![];
547 let mut snapshot = None;
548 while !self.eat(&token::CloseDelim(Delimiter::Brace)) {
549 if self.token == token::Eof {
552 if self.is_diff_marker(&TokenKind::BinOp(token::Shl), &TokenKind::Lt) {
553 // Account for `<<<<<<<` diff markers. We can't proactively error here because
554 // that can be a valid path start, so we snapshot and reparse only we've
555 // encountered another parse error.
556 snapshot = Some(self.create_snapshot_for_diagnostic());
558 let stmt = match self.parse_full_stmt(recover) {
559 Err(mut err) if recover.yes() => {
560 self.maybe_annotate_with_ascription(&mut err, false);
561 if let Some(ref mut snapshot) = snapshot {
562 snapshot.recover_diff_marker();
565 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
566 Some(self.mk_stmt_err(self.token.span))
569 Err(err) => return Err(err),
571 if let Some(stmt) = stmt {
574 // Found only `;` or `}`.
578 Ok(self.mk_block(stmts, s, lo.to(self.prev_token.span)))
581 /// Parses a statement, including the trailing semicolon.
582 pub fn parse_full_stmt(
584 recover: AttemptLocalParseRecovery,
585 ) -> PResult<'a, Option<Stmt>> {
586 // Skip looking for a trailing semicolon when we have an interpolated statement.
587 maybe_whole!(self, NtStmt, |x| Some(x.into_inner()));
589 let Some(mut stmt) = self.parse_stmt_without_recovery(true, ForceCollect::No)? else {
593 let mut eat_semi = true;
594 match &mut stmt.kind {
595 // Expression without semicolon.
597 if self.token != token::Eof && classify::expr_requires_semi_to_be_stmt(expr) => {
598 // Just check for errors and recover; do not eat semicolon yet.
599 // `expect_one_of` returns PResult<'a, bool /* recovered */>
600 let replace_with_err =
601 match self.expect_one_of(&[], &[token::Semi, token::CloseDelim(Delimiter::Brace)]) {
602 // Recover from parser, skip type error to avoid extra errors.
605 if let TokenKind::DocComment(..) = self.token.kind &&
606 let Ok(snippet) = self.span_to_snippet(self.token.span) {
607 let sp = self.token.span;
608 let marker = &snippet[..3];
609 let (comment_marker, doc_comment_marker) = marker.split_at(2);
612 sp.with_hi(sp.lo() + BytePos(marker.len() as u32)),
614 "add a space before `{}` to use a regular comment",
617 format!("{} {}", comment_marker, doc_comment_marker),
618 Applicability::MaybeIncorrect,
623 self.check_mistyped_turbofish_with_multiple_type_params(e, expr)
635 if replace_with_err {
636 // We already emitted an error, so don't emit another type error
637 let sp = expr.span.to(self.prev_token.span);
638 *expr = self.mk_expr_err(sp);
641 StmtKind::Expr(_) | StmtKind::MacCall(_) => {}
642 StmtKind::Local(local) if let Err(e) = self.expect_semi() => {
643 // We might be at the `,` in `let x = foo<bar, baz>;`. Try to recover.
644 match &mut local.kind {
645 LocalKind::Init(expr) | LocalKind::InitElse(expr, _) => {
646 self.check_mistyped_turbofish_with_multiple_type_params(e, expr)?;
647 // We found `foo<bar, baz>`, have we fully recovered?
650 LocalKind::Decl => return Err(e),
654 StmtKind::Empty | StmtKind::Item(_) | StmtKind::Local(_) | StmtKind::Semi(_) => eat_semi = false,
657 if eat_semi && self.eat(&token::Semi) {
658 stmt = stmt.add_trailing_semicolon();
660 stmt.span = stmt.span.to(self.prev_token.span);
664 pub(super) fn mk_block(&self, stmts: Vec<Stmt>, rules: BlockCheckMode, span: Span) -> P<Block> {
671 could_be_bare_literal: false,
675 pub(super) fn mk_stmt(&self, span: Span, kind: StmtKind) -> Stmt {
676 Stmt { id: DUMMY_NODE_ID, kind, span }
679 pub(super) fn mk_stmt_err(&self, span: Span) -> Stmt {
680 self.mk_stmt(span, StmtKind::Expr(self.mk_expr_err(span)))
683 pub(super) fn mk_block_err(&self, span: Span) -> P<Block> {
684 self.mk_block(vec![self.mk_stmt_err(span)], BlockCheckMode::Default, span)